Sliding-Mode-based Improved Direct Active and Reactive Power Control of Doubly Fed Induction Generator under Unbalanced Grid Voltage Condition

This paper proposes an improved direct active and reactive power control (DPC) strategy for a grid-connected doubly fed induction generator (DFIG) based wind-turbine system under unbalanced grid voltage condition. The method produces required rotor voltage references based on the sliding mode control (SMC) approach in stationary reference frame, without the requirement of synchronous coordinate transformation, and therefore causes a simpler design for power control system. Under unbalanced grid voltage condition, two control targets obtained simultaneously, i.e., removing stator active and reactive power oscillations. Moreover this method reduces the THD of stator current. Also it is shown that the proposed control method not only has a high-speed dynamic response but is stable during wind speed and system parameters variations. Simulation results for a 2kw DFIG confirm prominence of proposed control strategy.